#include<iostream>
#define N 100005
using namespace std;
struct node
{
	int b,e;
	int t;
};
node record[N];
bool vis[N]={false};
int main()
{
	int n,h;
	cin>>n>>h;
	for(int i=0;i<h;i++)
	{
		cin>>record[i].b>>record[i].e>>record[i].t;
	}
	int ans=0;
	for(int i=0;i<h;i++)
	{
		vis[record[i].b]=true;
		vis[record[i].e]=true;
	}
	int cut=0;
	for(int i=0;i<h;i++)
	{	
		int base=0;
		for(int j=record[i].b;j<=record[i].e;j++)
		{
			if(vis[j]==true)
			{
				base++;
			}
		}
		if(base>record[i].t)
		{
			cut+=(base-record[i].t);
		}
	}
	for(int i=0;i<n;i++)
	{
		if(vis[i]==true)
		{
			ans++;
		}
	}
	cout<<(ans-cut)<<endl;
	return 0;
}